Factor V Leiden: higher risk of thrombosis due to gene mutation

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What many do not know: Tiny injuries are constantly forming in the body, which are closed by small blood clots, but which dissolve by themselves without being noticed and without damage. Only if this does not happen can it become dangerous, especially if an embolism occurs. A vessel is closed by material that has loosened from a blood clot – pulmonary embolism, which is often fatal, is known above all. The cause lies quietly and dangerously in another part of the body; material from a leg vein thrombosis detaches and migrates through the blood vessels to the lungs, where it clogs the fine pulmonary arteries and can lead to asphyxiation.

So how does a small gene change lead to these dangerous blood clots? Factor V disease causes so-called APC resistance – a thrombophilia, as doctors call it, when the blood clotting is disturbed and the tendency to thrombosis is increased.

Various mechanisms work together in the body so that our vital blood clotting functions, for example to prevent bleeding to death in the event of injuries. In simple terms, coagulation factors are certain components of our blood (proteases) that become active when bleeding has to be stopped. When the coagulation factors are activated, a thrombus or clot forms – the blood coagulates. To prevent this from happening excessively, the clotting factors have antagonists (protease inhibitors), which ensure that the blood does not clot excessively and that a thrombus is broken down again when the bleeding has stopped.

In Factor V disease there is a mutation in the gene for coagulation factor V. Normally, factor V has an antagonist that reliably ensures that the blood does not clump excessively – the activated protein C (APC). Due to the mutation, the APC no longer has any effect on the coagulation factor V and can no longer inhibit it, so the blood coagulates excessively.

Background mutation: How is Factor V Leiden inherited?

Factor V ailments can be passed on to both mothers and fathers. Inheritance is autosomal dominant, which means that the mutation is “active” and the risk of thrombosis increases (approx. Five to ten times) if it was only received from one parent. If both parents carry the mutation, it is inherited from both parents. Then the risk of thrombosis is even higher than with simple inheritance (approx. 26-fold). Interestingly, factor V disease only occurs in people of European descent, i.e. Caucasians, the reasons are not clear, according to researchers, the first mutation carrier was probably someone in present-day Sweden around 25,000 years ago.

How can thrombosis from factor V disease be recognized?

Especially when people suffer venous thrombosis before the age of 45, doctors prick up their ears, even more when it seems to come from nowhere, i.e. when there are no additional risk factors. Typical thrombosis risk factors are according to the professional association of German internists:

• Blood clotting disorders – hereditary or acquired
• Infectious diseases, fever
• Operations
• Injuries
• Long-term overexertion
• Tumor diseases
• Prolonged bed rest or immobilization of an extremity (plaster cast)
• Pregnancy and childbirth (especially by caesarean section)
• Taking hormone preparations containing estrogen such as the “pill”
• Hormone replacement therapy for menopause

In general, the risk of thrombosis is particularly high when the blood builds up in the legs, such as when sitting for a long time on an airplane. The blood flow then becomes slower and, in addition, the blood becomes “thick” due to the dry air in the aircraft. The risk factors generally affect everyone, except that they often lead to thrombosis in people with factor V diseases or other thrombophilia, especially in the leg veins. These are not always easy to recognize, they can be expressed, among other things, by:

• Tension or pain such as sore muscles in the limbs (the discomfort decreases when the limb is raised)
• Swelling and protrusion of the veins that run directly under the surface of the skin compared to the opposite side
• Slightly bluish discoloration and possibly sensation of warmth in the affected limb
• Pressure pain on the inside of the foot
• Calf pain when flexing the foot or when applying pressure

However, these signs only occur in 50 percent of deep vein thromboses, warns the Professional Association of German Internists. That is why doctors rely on ultrasound and blood tests for diagnostics.

Warning, emergency: If chest pain and shortness of breath also occur, these can be warning signs of a pulmonary embolism. Then it is an acute emergency – so call the emergency doctor immediately on 112!

Whether factor V disease or another gene mutation was involved in the development of a thrombosis or embolism can only be found out through special blood and gene tests.

Detecting factor V diseases through blood tests and gene tests

Specialists – especially hematologists – carry out special tests to detect a factor V disease if there is a suspicion, which seems likely if the thrombosis patient has the following conditions:

• Thrombosis without an obvious trigger, such as pregnancy, bed restraint, etc.
• Thrombosis before the age of 45
• Close blood relatives who have already suffered thromboses or embolisms, especially if they were unusually young
• Thrombosis in unusual parts of the body
• Multiple miscarriages

First of all, the doctor can generally measure the blood coagulation. To do this, blood is drawn and the time it takes to clot under laboratory conditions is observed. Whether there is specific APC resistance, i.e. the coagulation disorder caused by factor V disease, can be tested if activated protein C is added to the blood. Normally, this should make the blood clot more slowly because activated protein C is an antagonist to blood clotting.

However, activated protein C has no effect on the blood of people with factor V disease because the mutation makes it resistant. However, in rare cases, APC resistance can also be due to another mutation, which is why a gene test is carried out to determine factor V disease. The genetic makeup is examined to see whether factor V disease is only present in the genetic makeup of one parent or in both. Depending on the situation, the risk of thrombosis is even higher.

Well-known factor V ailments: thrombosis prevention and pregnancy

Anyone who knows that they are carriers of factor V diseases must be particularly careful to keep the already increased tendency to thrombosis under control as much as possible. There is no special treatment for factor V disease or APC resistance. To prevent thrombosis, the following measures are particularly important:

• Maintain or achieve normal weight
• Do not smoke, do not consume alcohol excessively
• Drink enough water, at least 1.5-2 liters per day
• Regular exercise, preferably endurance sports such as jogging, walking or swimming
• Do not take any preparations containing estrogen, e.g. for hormone replacement therapy in menopause or birth control pills with estrogen
• With varicose veins or often “heavy legs”, go to the doctor for a vein check
• Regular blood check-ups

Pregnancy as a special case: Women with factor V disease are at increased risk of miscarriage and the development of thrombosis during pregnancy. You must therefore be monitored and cared for particularly closely, and according to a doctor’s assessment, you will receive anticoagulant medication (e.g. heparin) during pregnancy.

Read here how existing thromboses are treated with anticoagulants and other agents.

The effect of the hormones is important for the health of women not only in relation to the risk of thrombosis and cardiovascular diseases, the hormone balance can also get out of step during pregnancy and during the menopause. Our topic pages all have tips and backgrounds.

You can read everything you need to know about the warning signs here about the special thrombosis “sinus vein thrombosis”, which is actually very rare, but which recently occurred in connection with the AstraZeneca vaccination.

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